1. Field of the Invention
The present invention is directed to splittable optical-fiber ribbon products and, more particularly, to optical-fiber ribbon products containing a plurality of sub-unit ribbons that may be separated into fully functional, independent optical-fiber ribbons.
2. Related Art
In the related art, sub-unit ribbons include a plurality of optical fibers encapsulated in a matrix material. A plurality of sub-unit ribbons are then fully encapsulated together to form a splittable optical-fiber ribbon product. Although any number of sub-unit ribbons may be encapsulated together, only two sub-unit ribbons are shown in FIG. 6. As shown in FIG. 6, a first subunit ribbon 10xe2x80x2 includes a plurality of optical fibers 1xe2x80x2 which are encapsulated by matrix material 2xe2x80x2. Similarly, a second sub-unit ribbon 20xe2x80x2 includes a plurality of optical fibers 1xe2x80x2 which are encapsulated by matrix material 2xe2x80x2. The first and second sub-unit ribbons 10xe2x80x2, 20xe2x80x2 are then fully encapsulated by encapsulation material 30xe2x80x2 to form a splittable optical-fiber ribbon product.
A continuing problem in the development of optical-fiber cables is that of providing a high fiber count in a small cable volume in an effort to reduce costs. The related art splittable optical-fiber ribbon product suffers disadvantages in this regard. First, the encapsulation material 30xe2x80x2 increases the width and thickness of the splittable optical-fiber ribbon product, thereby allowing a limited number of optical fibers 1xe2x80x2 to occupy a given volume. The width of the splittable optical-fiber ribbon product is the widths w1 and w2 of the first and second sub-unit ribbons 10xe2x80x2 and 20xe2x80x2, plus twice a hinge thickness th of encapsulation material 30xe2x80x2, which hinge thickness th exists on each side. Therefore, the width of the splittable optical-fiber ribbon product is increased by at least twice the hinge thickness th over the width of an optical-fiber ribbon made without sub-units and having the same number of fibers as the two subunits 10xe2x80x2 and 20xe2x80x2 together. Similarly, the encapsulation material 30xe2x80x2 is present on the top and bottom of the sub-unit ribbons 10xe2x80x2, 20xe2x80x2 as an overcoat having thickness to. Therefore, the thickness of the splittable optical-fiber ribbon product is thicker than either sub-unit by an amount that is twice the overcoat thickness to.
Further, the individual sub-units may be thicker and wider after being separated or split from the splittable ribbon than before they were joined together. Therefore, the remaining matrix material on the separated sub-units must be removed, which causes additional time delays when it is desired to use the sub-units as individual ribbons, as in connectors and other equipment, for example, after they are separated from the splittable optical-fiber ribbon product.
This increased width and thickness results in a lower packing density, i.e., a smaller fiber count within a particular volume for the splittable optical-fiber ribbon product as well as for the individual sub-units after they are split from the ribbon product.
In order to increase packing density, one related art solution involves using the encapsulation material to provide hinge coverage in the splittable optical-fiber ribbon product. That is, in this type of related art product, the individual sub-units do not have a matrix material which completely encapsulates the optical fibers. Instead, the optical-fibers are completely encapsulated only after the encapsulation material is applied. This arrangement thus attempts to increase packing density by eliminating the sub-units"" hinge thicknesses. When the sub-units are split, however, there is a distinct danger of having one of the fibers on either end of the sub-unit break out of the sub-unit package. This danger is especially acute on the end of the sub-unit that was previously adhered to another sub-unit because the sub-unit hinge is too thin to have the strength necessary to withstand the forces involved in the process of fracturing the encapsulation material that binds it to the adjacent sub-unit.
Another problem related to fully encapsulating the sub-unit ribbons is high cost in both materials and production of splittable optical-fiber ribbon products. That is, the encapsulation material 30xe2x80x2 can be quite expensive and, therefore, the more that is used, the more expensive the end product becomes. Further, the encapsulation material is typically cured using ultra-violet (UV) or other radiation. And the amount of energy required to cure the encapsulation material 30xe2x80x2 is proportional to the amount of material used.
Yet another problem in the optical-fiber industry is that of easily and quickly accessing the optical fibers within a splittable optical-fiber ribbon product. That is, for installation, service and maintenance purposes, it often becomes necessary to perform splicing and termination operations on individual optical-fibers within a splittable optical-fiber ribbon product. In order to access the individual optical-fibers, a peeling process is typically used. The peeling process must leave the optical fibers with their individual coatingsxe2x80x94including color coatingsxe2x80x94intact, yet peel away all of the sub-unit""s matrix material that binds them together. The sub-units of splittable ribbon products are easily split away from the combined optical-fiber ribbon product to facilitate access in the field. However, difficulty arises in that both an encapsulation material and a sub-unit matrix material must then be peeled off in order to access individual fibers. This situation will be described with reference to FIGS. 7 and 8.
FIG. 7 shows a first sub-unit ribbon 10xe2x80x2 after it has been split apart from the combined optical-fiber ribbon product shown in FIG. 6. As shown in FIG. 7, the sub-unit 10xe2x80x2 and the optical fibers 1xe2x80x2 are still encapsulated within encapsulation material 30xe2x80x2 as well as within matrix material 2xe2x80x2. Therefore, a two-step peeling process often must be performed to access the optical fibers 1xe2x80x2. That is, a first peeling process performed on the split-off sub-unit 10xe2x80x2 shown in FIG. 7 typically results only in removal of the encapsulation material 30xe2x80x2 leaving the sub-unit 10xe2x80x2 as shown in FIG. 8. A second peeling process must then be performed on the split-off sub-unit 10xe2x80x2 as shown in FIG. 8 to remove the matrix material 2xe2x80x2 so that the optical-fibers 1xe2x80x2 can be accessed.
Performing two peeling processes to access the optical fibers 1xe2x80x2 adds to installation time for workers in the field who are using such ribbons. When applied to high fiber-count installations, this added installation time can become quite sizable.
It is an object of the present invention to overcome the drawbacks of the related art. More particularly, it is an object of the present invention to provide a lower cost splittable optical-fiber ribbon product than that available in the related art, and one which also reduces external dimensions in order to increase its packing density, i.e., the space required to pack a stack of ribbons in a cable or tube. Reducing external dimensions reduces cost and increases packing density, thereby allowing a high fiber count to be provided in a small cable volume.
It is another object of the present invention to reduce the risk of fiber breakout in splittable optical-fiber ribbon products.
It is a further object of the invention to provide a splittable optical-fiber ribbon product in which individual optical fibers can be accessed easily and quickly. More particularly, it is an object of the present invention to provide a splittable optical-fiber ribbon product whose optical fibers can be accessed with only one peeling process, thereby reducing installation time in the field.
The present invention achieves the above and other objects and advantages by not fully encapsulating a splittable optical-fiber ribbon product""s sub-unit ribbons. Instead, adhesion matrix material, bonding material, or adhesive is applied only to the area in the gap between sub-units of a splittable optical-fiber ribbon product, and the sub-units themselves include a matrix material which encapsulates the individual optical fibers. The adhesion properties of the adhesion matrix material are such that when cured, it adheres well to all of the sub-units and, thus, effectively creates one ribbon. It is important to emphasize that the bond between the adhesion matrix material and the sub-unit matrix material must be sufficiently strong so that outward normal forces applied to the external surface of the adhesion matrix material are transferred to the sub-unit matrix material. If this bond is sufficiently stronger than the similar bond existing between the sub-unit ribbon matrix and the individual fibers"" secondary coating, then the outward normal forces applied by the peeling process will cause a break in to occur at the interface between the sub-unit matrix and the individual fibers, rather than between the sub-unit matrix and the adhesion matrix material. Additionally, the adhesion matrix material is sufficiently brittle so that the final product can easily be split into respective sub-units, yet is sufficiently tough that the finished product does not break apart during the cabling process. The combination of the edge-bondedxe2x80x94not fully encapsulatedxe2x80x94design and the choice of adhesion matrix material for optimized adhesion properties allows for the achievement of the desired final ribbon properties. This is because normal manufacturing process variations may allow for the adhesion matrix material to be applied in locations other than in the interstitial gap between sub-units. For example, if the adhesion matrix material is present on the top surface of ribbon, due to normal production variations, the transfer of normal forces on this adhesion matrix layer to the sub-unit matrix layer will improve the peel performance and allow the one step peel process to be accomplished.
The adhesion matrix material in the present invention may be any UV or other radiation-curable acrylate, as is typically used in the optical-fiber industry. Examples of the adhesion matrix material according to the present invention are DSM-C9-32 available from DSM Desotech Incorporated, Borden 255 UV-curable acrylate, or any minor variation of these or similar materials. It is understood that the adhesion matrix material must be of similar composition as the sub-unit matrix material, however, the minor variations possible might include formulation changes for promoting adhesion, for altering the brittleness, or any other material property variation deemed desirable.
Although it is preferable to use an adhesion matrix material which is the same as that of the sub-unit matrix material, different materials may by used for each. However, the adhesion matrix material must be sufficiently similar to the sub-unit matrix material so that it forms a strong enough bond to hold the sub-units together during processing and handling. Further, the adhesion matrix material may be a color different from that of the sub-unit ribbons"" matrix material so that the sub-units can be easily identified and, therefore, easily split-off from the splittable optical-fiber ribbon product.
A negligible thickness of the adhesion matrix material may, or may not, exist across the external surfaces of the sub-unit, as on the top, bottom and hinge ends of the sub-units. However, the only appreciable buildup of this material is in the interstitial gap between the sub-units. The sub-units themselves can, therefore, be manufactured such that their dimensions are identical, or nearly identical, to the dimensions of any standard ribbon of similar fiber count that is manufactured for independent use, i.e., a ribbon that is not of a splittable-type.
Because a splittable optical-fiber ribbon product""s sub-unit ribbons are not fully encapsulated by encapsulation material, the splittable optical-fiber ribbon product of the present invention allows a tighter packing density than a fully encapsulated ribbon. This means that the same number of ribbons, with identical fiber counts, can be packaged in a tube or cable having a smaller diameter than that made with the conventional splittable optical-fiber ribbon products. Further, the sub-unit ribbons have a tighter packing density after they have been separated from the splittable optical-fiber ribbon product.
Additionally, using sub-units that fully encapsulate their optical fibers, sub-unit geometrical independence is maintained and the adhesion matrix material is used merely to adhere sub-units together. Such allows for a reduced risk of having end fibers break out during or after a sub-unit has been split apart from the splittable optical-fiber ribbon product. Such also allows the sub unit ribbons easily to be used in standard connectors or other apparatuses designed for independent-use ribbons, i.e., ones which are not of a splittable-type and, therefore, do not have the additional thicknesses th and to.
Further, because a splittable optical-fiber ribbon product""s sub-unit ribbons are not fully encapsulated by encapsulation material, a substantially smaller volume of a rather expensive material is required, and the sub-units are more easily separated into independent, fully functioning, sub-units when it is desired to do so.
Moreover, according to the present invention, because a splittable optical-fiber ribbon product""s sub-unit ribbons are not fully encapsulated by encapsulation material, a peeling process to access individual fibers is simplified and shortened. That is, only one step is necessary to peel the splittable optical-fiber ribbon product of the present invention, thereby reducing installation, service and maintenance time.